The Queen and senior royals led the service celebrating the Commonwealth in London.

Kate and William joined the Queen and the Duke of Edinburgh as well as Prince Charles and the Duchess of Cornwall for the Commonwealth Observance.

It was the first time that William and Kate have attended the event, held at Westminster Abbey, which celebrates the multinational organisation on Commonwealth Day.

The royals were joined by politicians including the president of Sri Lanka, Maithripala Sirisena, plus High Commissioners, other Commonwealth dignitaries, faith leaders and more than 1,000 children.

The royal party was introduced to a line-up including Mr Sirisena and his first lady, plus Commonwealth secretary-general Kamalesh Sharma and senior Abbey clergy.

William and Kate, who arrived first, chatted with Charles and Camilla as they waited for Philip and the Queen, who wore a pale beige summer tweed dress and coat by Karl Ludwig and a matching hat by Angela Kelly.

They then joined a procession that included a group of Brownies, down the nave of the historic ecclesiastic building before the Queen's Commonwealth Day message was played via giant screens.

In the message, which is also being broadcast by radio in Commonwealth states today, the Queen hailed its continued role, saying what the member states share is more important now than at any point in its history.

She said the 53 nations, whose combined populations total 2.2 billion people, are "guardians of a precious flame" with an obligation to keep it burning brightly for decades to come.

Her Majesty warned that "when common goals fall apart, so does the exchange of ideas. And if people no longer trust or understand each other, the talking will soon stop too".

She added that the organisation's members have drawn on their shared history to act on the "huge advantages of mutual co-operation and understanding" to the benefit of their citizens.

The annual event, which has the theme of "a young Commonwealth", also featured dancing, hymns and readings.